1. Field of the Invention
This invention relates generally to draft inducers for hot water heaters. More particularly, the present invention relates to blower designs for cooling electric motors placed inside blower housings.
2. Description of Related Art
Typical blower housing and motor assemblies, particularly with respect to centrifugal fans having radial-flow impellers, are configured with the motor being attached to an end of a circular or scroll-shaped blower housing. The motor's shaft extends axially into the housing where an impeller, confined by the blower housing, is attached to the motor shaft. The blower housing typically has one inlet and one outlet. Combustion gases are drawn into the housing by the rotating impeller which expels the gases through the outlet into a flue or similar avenue of exit.
With respect to motor cooling, the gases that are forcibly moved through the housing by the impeller do not come into contact with the motor. Thus, blower activity does not in any way contribute to the cooling of the motor.
Due to the inevitable generation of heat by an operating motor, a means for cooling the motor during operation is needed. Conventional blower/motor assemblies have one or two auxiliary fans attached to the rotor to draw motor-cooling air into the motor housing. Vents are provided in the motor housing to enable air infiltration. The incoming air is channeled around the motor windings and out the same vents.
Another approach for providing cooling air to a blower motor is described in U.S. Pat. No. 5,352,099 to Anstine et al. In the '099 patent, a blower having an optional one-piece motor/impeller housing with a cover is suspended above the flue pipe of a water heater with brackets. The inlet of the blower housing is situated in axial alignment with the water heater exhaust flue. Vents situated in the motor portion of the blower housing allow cooling air to be drawn over the motor and expelled out an outlet through which the exhaust gases drawn into the blower are also expelled.
This approach to introducing cooling air into the blower has numerous problems which effect both the overall efficiency of the blower and the ability to effectively cool the motor. By having the blower housing suspended over the flue pipe, it is very difficult to establish the negative pressure necessary to draw in the flue gases for expulsion from the water heater. The lack of negative pressure results from the lack of a containment area or enclosure that enables the rotating impeller to generate the necessary negative pressure.
An additional problem encountered with the '099 patent design is the inability to control standby losses when there is no demand placed on the water heater. With the flue open to the atmosphere, i.e, below the blower, absent blower activity, flue gases and heat generated during standby cannot be controlled.
A further problem is the inability to control the dilution air flow. The "open" concept of the '099 patent suspended blower design prevents any appreciable control over the flow of dilution air other than by altering the rotational velocity of the impeller. Altering impeller velocity, however, can have a negative effect on efficiency.
Although numerous blower housing designs have been developed to address motor cooling, none to date have the capability to provide a controlled amount of cooling air to the blower motor without the need for auxiliary fans attached to the motor. None have devised a blower housing that is easy and cost-effective to manufacture such that the dilution air flow can be controlled to balance the need for exhaust gas expulsion and the need for motor cooling. None have devised a blower housing that can accomplish these tasks as well as provide ease of assembly and disassembly for maintenance purposes. A way to provide all these advantages has now been developed.
It is, therefore, an object of the present invention to provide a blower housing assembly that reduces the number of components necessary to provide a functioning blower. The need for separate motor and impeller housing is obviated.
Another object of the present invention is to provide a blower housing that allows the negative pressure generated by a rotating impeller to draw cooling or dilution air into the motor chamber to cool the motor.
An additional object of the present invention is to provide a blower housing with a skirt extending past a blower housing cover for attachment to the top of a hot water heater to facilitate and maximize the potential to draw exhaust gases out of and away from the hot water heater.
A further object of the present invention is to provide a blower housing design that allows for the control of dilution air added to the exhaust gases emanating from a hot water heater to reduce the overall temperature of the mixed gases to an acceptable level.
A still further object of the present invention is to provide a cost-effective blower housing that is easy to manufacture and requires no additional parts beyond a housing body and a housing cover. These and other objects of the invention will be made apparent from a review of the drawings and a reading of the following summary and detailed description of the invention.